The objective of this proposal is to define structure-function relationships in proteins as fully as possible in terms of their modes of internal motions, electrostatic interactions and specific structural adaptations. The motional analyses are based primarily on nuclear magnetic resonance studies of 13C relaxation processes at more than one field strength, in some cases at natural abundance of the 13C isotope and in others after incorporation of enriched amino acid residues by semisynthetic techniques. The electrostatic interactions will be analyzed in terms that take account of the degree of solvent accessibility of the charge loci. The analyses are based on structural data provided by x-ray crystallography from other laboratories and involve correlation with observed pK values, titration curves at various ionic strengths, pH dependence of stability, stabilization of oligomers, binding of effectors, and so on. The primary experimental emphasis will be on a group of myoglobin species representing a relatively closely related range of sequence variants augmented by some semisynthetic variants, and on some selected hemoglobin forms. Other proteins will be studied to explore various aspects more fully, especially with respect to electrostatic phenomena. The myoglobins and hemoglobins will be studied in terms of their specific functional properties including ligand binding thermodynamics, buffering behavior, stability, and allosteric effector interactions.